1. Technical Field
The present invention relates to a semiconductor circuit, and more particularly, to a semiconductor integrated circuit.
2. Related Art
A semiconductor integrated circuit may be manufactured is with various memory capacities and input/output modes.
A conventional semiconductor integrated circuit such as, for example, DRAM may be configured as X8—512M, X16—512M, and X16—256M.
X8—512M is a 512 Mb DRAM with eight input/output data terminals DQ0 to DQ7. Similarly, X16—512M 512 Mb DRAM with 16 input/output terminals DQ0 to DQ15, and X16—256M is a 256 Mb DRAM with 16 input/output terminals DQ0 to DQ15.
According to a specification of the semiconductor integrated circuit as shown in FIG. 1, X8—512M uses row addresses A0 to A13 and column addresses A0 to A9, X16—512M uses row addresses A0 to A12 and column addresses A0 to A9, and X16—256M uses row addresses A0 to A12 and column addresses A0 to A8.
As shown in FIG. 1, when the number of column addresses is reduced by one bit, half of the X16—512 Mb DRAM may be operated as X16—256M.
A conventional semiconductor integrated circuit includes a pad IOX8 to select either a X8 or X16 input/output mode.
Referring to FIG. 2, X8—512M fixes the pad IOX8 to a logic high level, and X16—512M and X16—256M fix the pad IOX8 to a logic low level.
Furthermore, since X8—512M uses a row address A13, X8—512M controls the corresponding pad to receive the row address A13 from outside. Since X16—512M and X16—256M do not use the row address A13, X16—512M and X16—256M float the corresponding pad.
The conventional semiconductor integrated circuit uses a fuse circuit provided therein, in order to support various products such as X8—512M, X16—512M, and X16—256M. In particular, the fuse circuit is used to support 256 Mb DRAM using 512 Mb DRAM. That is, the type of a product may be defined by blowing a fuse of the fuse circuit or not.
However, the fuse cannot be restored to the original state after it is blown. That is, only 256 Mb of 512 Mb may be used after the corresponding fuse is blown.
Therefore, since the conventional semiconductor integrated circuit decides a memory capacity through a fuse, it is difficult to change the quantity of products shipped to deal with changing demand.
Whether or not to blow a fuse is determined during a probe test. In this state, it is difficult to estimate the demand, that is, determine whether to use 256 Mb or 512 Mb. Furthermore, the fuse may cause problems during a blowing process, thereby reducing the reliability of the semiconductor memory integrated circuit.